The proposed research is designed to furnish quantitative and qualitative information about the fate of inhaled coal dust from different sources when laboratory animals are exposed for periods up to six months. The pulmonary alveolar macrophages will be harvested and analyzed for their capacity to phagocytize and their lysosomal enzymes activity. In addition, the total quantity of coal dust present in the lungs will be determined. The coal particles harvested, after enzymatic digestion of the lungs, will be analyzed for their particle size distribution and their metal content. Lung sections will be studied for histopathological changes. It isexpected that the information from animals will be extrapolated for the evaluation of hazards to man.